The Civilab Slake Durability Apparatus can be supplied with two or four drives, providing for up to four tests to be run simultaneously and comprises an inbuilt automatic minute timer. The apparatus measures the speed of the breakdown when a sample is subjected to a standard drying and wetting cycle. A sample of ten representative rock lumps, each weighing 40-60 grms, is oven dried and placed in the test drum. The drum is then half immersed in a water bath and slowly rotated for ten minutes. The fine products of this slaking process pass through the sieve mesh that forms the body of the drum. The slake durability is calculated by expressing the specimen retained in the drum as a percentage of the original sample.